For each kind of plastic and plastic parts, there is a temperature limitation on mold surface, once exceed the limitation, one or more adverse effects may appear. The higher temperature of
mold is, the smaller flow resistance will be. In a number of injection molding machine, this naturally means faster passing through the water, the runner and cavity, because the injection flow control valve will not correct the change, filling faster will cause higher effective pressure in the runner and cavity. And it may cause flash. Due to the fact that hotter model does not freeze plastic materials that enter into the area of the overflow before high voltage produces, molten material can flash around the ejector rod and overflow into the line clearance. This suggests that good injection rate control is a must, and some modern flow control programmer indeed can make it.
In common sense, the rise of mold temperature will reduce condensation layer of plastic in cavity, making molten material within the cavity flow more easily, thereby gaining more weight and better surface quality of parts. Meanwhile, increase of mold temperature will increase tension strength the parts. Many moulds, especially engineering thermoplastics, run at relatively higher temperatures, if there is no heat preservation for moulds, heat lost into the air and the heat in
injection molding machine can be easily equal to the loss of plunger cylinder. So the mould and board should be insulated, if possible, surface of the mould should be insulated. If consider using a hot runner mold, try to reduce the heat exchange between hot parts and cooling parts of the injection moulds. This method can reduce both energy loss and preheating time.
